Gas valves is widely used in kitchen to control the gas open or close (here gas means coal gas and natural gas). We know gas is dangerous in case it leaks,so how to choose good quality gas valves is very important for our life. Come on, follow me please! First,Please check if the gas valves has been certified by CSA or any other famous company, then check the list number on their website to make sure if it is true. Both of them works means the quality of the good shall be good. Second,if the good you find has not been certified by any famous company, don`t worry, we also can keep finding as below: 1)Check the the handle of gas valve, if the material is stainless steel 304. that means best if the material is steel with chrome plated, then the quality is good if the material is steel with nickle plated, then the quality is unsure, then we look next: 2)Check the drawing which is coming with the gas valve, if the gas valve is seal by TWO O-rings, that means good. 3)Check the seat ring beside the ball, if the seat ring is made by PTFE not plastic, that means good 4)If you can,check the ball, it should be very smooth, that means good 5)Check the body of the valve, if it has been heat treatment, that means good. 6)Turn on or off the handle of the valve, if you feel smooth but a little tight, that means good. Above are all my experiences that maybe will help you when choosing gas valves. good lucky!